Rotating a solution for a sufficient period of time in an ultracentrifuge gives rise to a sedimentation-diffusion equilibrium. The denser component in the solution sediments in the direction of the field, and back-diffusion occurs in response to the non-uniform concentration. At equilibrium the concentration of the solute increases with distance from the center of rotation and gives rise, along with the compression, to a density gradient. In conventional sedimentation equilibrium experiments described by Svedberg and Pedersen (68), and by Schachman (56), performed with low concentrations of solute, the density gradient is small. However, when a concentrated solution of an appropriate low-molecular weight solute is used, a large density gradient may be established. Because the system is at equilibrium, the density gradient at any position in the liquid is stable and reproducible, and depends only on the angular velocity, distance, temperature, and the molecular and solution parameters of the system.


Density Gradient Deoxyribonucleic Acid Liquid Column Buoyant Density Analytical Ultracentrifuge 
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Copyright information

© Springer-Verlag in Vienna 1962

Authors and Affiliations

  • Jerome Vinograd
    • 1
  • John E. Hearst
    • 1
  1. 1.PasadenaUSA

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